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Subject: Re: Quick question on Killer heuristic

Author: Robert Hyatt

Date: 15:20:36 05/03/00

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On May 03, 2000 at 14:31:19, Dan Newman wrote:

>On May 02, 2000 at 21:29:46, Robert Hyatt wrote:
>
>>On May 02, 2000 at 20:35:09, William Bryant wrote:
>>
>>>In my program my killer table is simply an array of [ply][2] with two killers
>>>allowed per ply.  When updating the killer table, I replace the first killer
>>>with the new one (assuming it is not the same move), and move the old first
>>>killer to the second killer position, dropping what ever move is in the second
>>>killer position.
>>>
>>>In the introductory paragraphs of Ernst's book, he describes using counters
>>>to order the killer moves (page 23)
>>>"The killer moves carry "hit" counters with them which specify their priorities
>>>for sorting and replacement."
>>>
>>>This would, of course, require a larger table, and more time spent updating
>>>and sorting the killer table.
>>>
>>>Is this more efficient or effective than a standard replace table?  Other
>>>thoughts or comments about organizing the killer moves?
>>>
>>>Thanks.
>>>
>>>William
>>>wbryant@ix.netcom.com
>>
>>
>>I use counters...  I think this is the right way to do this...
>
>Bob,
>
>I just looked at Crafty v17.10 (to see if and where you zero the counters)
>and didn't see them.  I suspect you got rid of the counters when you went
>SMP (otherwise you'd have to do some locking to keep the counters and moves
>coherent, I suppose).  [I've been zeroing the counters in my program in the
>wrong spot I think...]
>
>-Dan.


you are right.  I don't know when I did that.  I now just always add a new
killer by bumping #1 to #2, and #2 out.  Unless the move is already in the
list in the #1 spot.  Then I leave it alone.

I'm not sure when I did this.  But for your question of zeroing the counts,
I did it in search...  when I entered search, I would clear killer_count[ply+1]
(the next ply's counters).




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